Paper manufacture



Patented Feb. 21, 1933 1 UNITED STATES PATENT OFFICE HAROLD ROBERT BAFTON, OF ANDOVER, MASSACHUSETTS, ASSIGNOR TO RUFOLD PROCESS CORPORATION, A CORPORATION OF MASSACHUSETTS PAPER MANUFACTURE No Drawing.

- This invention relates to the manufacture of paper filled with alkaline filler.

The principal object of this invention is to provide a method for improving the sizing of paper filled with alkaline filler.

An important ob ect is to provide improved conditions for machine operation in and the like are added to a fibrous mix under conditions favoring the minimizing of the time and/or intimacy of contact of the constituents of the mix, e. g. at the wet end of the paper machine. Cross reference is made in particular to the copending applications Serial No. 304,167, filed September 5, 1928,

.and Serial Nos. 321,753 and 321,754, both filed November 24, 1928.

a In my 'copending application Serial No. 428.231filed February 13, 1930, I have shown that it is desirable in certain cases to add an acidic material such as alum to alkaline filler just prior to the addition of said filler at the wet end of the paper machine. Reference is made to said application for a complete discussion of methods of test and paper machine cycles', which also apply in the present instance. As has been discussed in full in my said 'copending application, this pretreatment of alkaline filler with alum has been found to have a very beneficial effect both in the running of unsized and sized papers as it lowers the pH of the alkaline filler used therein.

I have now found that a similar beneficial effect and sometimes even an, improved effect, particularly when sized paper is made, can be obtained by pretreating an alkaline filler with precipitable material and a precipitant therefor. This pretreatment or protection of the alkaline filler should take place just prior to the addition of the alka- Application filed April 28, 1931. Serial No. 583,571.

line filler to the paper mix under conditions favoring the minimizing of the time and/or intimacy of contact of the constituents of the mix, i. e. preferably at the wet end of the paper machine. It is preferable that the precipitable material be so chosen as to produce a precipitate of relatively large covering power, and preferably one which is of itself acidic or at least'neutral in nature. For

example, a soap or'size such as rosin size is suitable. Also an alkali metal salt such as sodium silicate or sodium aluminate is a convenient material to use. In either case a suitable precipitant, preferably an acidic material, particularly a metallic salt such as alum,

may be employed, in stoichiometrical excess, if desired.

I have found that the formation of a rotective precipitate such as above descrlhed upon an alkaline filler in a liquid medium such as water is very different in its final result from the formation of a similar preei itate upon a substantiall inert filler such or example as clay, talc, ca cium sulphate or the like, even though such filler be slightly soluble such for example as 'is calcium sulphate. The difference is this: a precipitate formed on substantially inert filler, even though the filler remain in contact with water, is substantially permanent chemically and its pH 'value remains substantially unaffected by the filler. Thus a neutral precipitate on such filler remains substantially neutral and an acidic precipitate remains substantially acidic in nature. Orr the other hand any precipitate of an acid or neutral nature precipitated upon an alkaline filler in contact with water tends to be acted upon at once by the alkaline filler, because of the alkaline nature of such filler, in such a way that the precipitate is after a short time changed in respect to its acidic or neutral nature, its H being grad-' ually raised until it comes wit in the alkaline range, i. e. until its pH rises above 7.0. In

certain cases this tends completely to alter the nature of the precipitate and in certainother cases it tends substantially to modify it. As

the usefulness of such a precipitate in pro-- tecting alkaline filler depends upon its abllity substantially to lower the pH of the alkaline filler it becomes apparent that such a useful protective efiect in respect to alkaline filler is only temporary whereas the protective effect obtained upon fillers of an inert nature is substantially permanent. It will thus be evident that in' order that the protective effect on an alkaline filler be usefully employed, means must be adopted to utilize the alkaline filler in its temporarily protected condition before such temporary protection has been substantially or completely deteriorated.

In my copending application Serial No. 428,231 I disclose the fact that addition of acidic material such as alum to an alkaline filler gives the filler a temporarily acidic or neutral pH, but that this pH gradually reverts to a substantially permanent pH of about 8, which however is below the original pH of the filler. Likewise an alkaline filler protected as described herein will have a somewhat lowered permanent pH, but it is the temporarily substantially lowered pH which is of particular significance in the present invention.

In the preferred practice of my invention I mix with an alkaline filler, preferably when the same is in aqueous suspension, a solution of precipitable material such as rosin size, and then add to the mixture, just prior to its addition to a fibrous mix at the wet end of the paper machine, a solution of precipitant such as alum, which-acts to precipitate the size upon the alkaline filler and thus to produce a temporarily protected alkaline filler.

The size may be mixed with the filler at any time prior to use, but the alum should be added preferably continuously to the already mixed alkaline filler and size in a manner such that it is suitably mixed therewith just i 40 prior to the addition of the alkaline filler at the wet end of the paper machine, where the filler is usually added continuously. It is to be noted that agitation speeds up the rate of 4 the deterioration of the protection of the temporarily protected alkaline filler, particularly when such an alkaline filler is in concentrated suspension, and hence violent agitation of the already protected filler before addition to the paper mix should be minimized as much as ossible. The pH of the mixture will be relatlvely lower immediately after the alum addition than it will be after a few moments, but I have found that the temporarily protective effect on the filler persists for a sufficiently long time after it has been added tothe fibrous mix for said mix to pass over the web forming device and through the press rolls, and also for this effect to be maintained in a substantial degree in the circulating white water, i. e. tray water. It is also feasible to effect the precipitation at any time prior to the addition of the filler to the paper mix, provided that a further quantity of precipitantbe added just prior to such addition.

eas es use, and which permit of an economical prac tice of the invention, are approximately 2% size and 4% alum, calculated as the dry weight of the commercial materials on the dry weight of the alkaline filler employed. However in certain cases, especially where heavily sized papers are desired, I have increased the percentage of size and size precipitant greatly above this amount, having used, for example, 10% size and 10% alum in certain cases, and in other cases even more than this, with excellent results.

In making ordinary grades of sized paper,

it is customary to use in the neighborhood of 10 to 15% of filler in the furnish. Whereas I do not restrict myself to the use of these percentages I shall however use the 15% figure for the purpose of the following illustrative computation relative to size and alum. If size be used in the amount of 2% and alum in the amount of 4% on the 15% filler content of the furnish it will be evident that the size and alum based on the total furnish will be present in the amount of .3% and .6% respectively on the weight of the total furnish. Inasmuch as papers containing this amount of filler require ordinarily up to approximately 2% of size and 3% of alum based on the total furnish, it will thus be seen that if part of the size and alum required be used with the filler, the remainder may be used to size the fibre. For example, in my copending application Serial No. 304,167 referred to above, an alkaline filler is added at the wet end of the paper machine to previously sized fibrous material. In the case where the present procedure is used with that previous invention, the fibremay be sized with the major part of the size and alum in the beater, and then the filler, temporarily protected with the remaining size and alum, may be added to the presized fibre at the wet end of the paper machine with excellent results.

In my various copending applications referred to herein as well as in numerous others I have discussed in full the principle on which the expression minimizing the time and/or intimacy of contact is based. Briefly it is that alkaline filler, which always exists in the mix in great stoichiometrical excessover the acidic constituent, acts upon the acidic constituent to the ultimate destruction thereof and/or the destruction of the effect maintained by such constituent. This action has been found to depend upon the time of con tact of the acidic and alkaline constituents and also on the intimacy of contact of these constituents. Agitation such as normally occurs in papermaking procedure in stuff chests or the like accelerates the rate of reaction, but agitation at low concentrations while having some effect is not nearly so deleterious. Based on this principle a practical application has been developed whereby, by minimizing the time and/or intimacy of contact of the acidic and alkaline constituents, the acidic constituent and/or the effect produced thereby, is substantially preserved in an alkaline filler mix. With the present types of paper machines and the present arrangement of apparatus usually employed in paper machine operation, the contact of the acidic material and the alkaline constituent at any time prior to the passage of the stock from the last stuff chest, which is commonly called the machine chest, results in great deterioration or complete destruction of the acidic material. Addition of one or both of these constituents at a point subsequent to the passage of the stock from the machine chest, after which point according to present day operating practice the stock remains in concentrated condition only for a very brief interval of time, or addition preferably at or subsequent to the point of dilution, i. e. at the wet end of the paper machine, serves to substantially conserve the acidic material and/or effect thereof in the fibrous mix.

As precipitable material, instead of a soap or size or alkali metal salt such as sodium silicate or aluminate referred to above, I may use emulsions of various types such for example as emulsions of thermoplastic material such as parafline, or emulsions of other materials which are substantially inert to alkaline filler.

For precipitant I may use alone or in combination acidic materials, such as a mineral or other acids, metallic salts such as compounds of aluminum, zinc, tin, calcium, magnesium, or the like, and in certain cases, for example such as when sodium silicate is used, I have found it convenient to use the ammonium salts as precipitants thereof, usually in conjunction with an acidic material,

The term paper mix as used herein is intended to mean a mix of various constituents including fibre from which paper may be made, either alone or after the addition of other ingredients.

By the term alkaline filler I mean substantially water insoluble filler which when agitated in contact with freshly boiled distilled water, say for an hour, will impart a pH value to such water greater than 7.0, that is, which will be on the alkaline side of the neutral point. Among fillers included in this group may be mentioned calcium carbonate, of which lime mud from the causticizing process is one form; calcium carbonate magnesium basic carbonate employed in the paper disclosed in my U. S. Patent No. 1,595,416 of August 10, 1926; calcium carbonate magnesium hydroxide disclosed in my U. S. Patent N 0. 1,415,391 of May 9, 1922; and other substantially water insoluble normal or basic carbonates of alkaline earth metals, (which expression is herein intended to include magnesium), or compounds, double salts or physically associated mixtures of these with one or more other acid soluble materials of a substantially water insoluble nature.

When I use the word paper herein, I use it in the broad sense to include products of manufacture of all types and of all weights and thicknesses, which contain as an essential constituent a considerable amount of prepared fibre and which are capable of being produced on a Fourdrinier, cylinder, or other forming, felting, shaping or molding machine.

By the term wet end of the paper machine I intend to include those instrumentalities employed in paper manufacture by which and/or in which a relatively concentrated paper mix is diluted, and treated, conveyed or fed up to the point of web-formation, such as the mixing box, regulating and proportioning devices, rifliers, troughs, screens, head boxes, inlets and the like, ineludingv also instrumentalities used in the white water cycle.

It is to be understood that my invention is not dependent upon or limited by any theory expressed herein.

While I have described in detail the preferred embodiments of my invention, it is to be understood that the details of procedure, the proportions of ingredients, and the arrangement of steps may be widely varied without departing from the spirit of my invention or the scope of the subjoined claims.

I claim:

1. In the manufacture of paper filled with alkaline filler wherein alkaline filler is added to a paper mix under conditions favoring the minimizing of the time and/or intimacy of contact of the constituents of the mix, that step comprising effecting the precipitation in the presence of said alkaline filler of a precipitable material and a precipitant therefor prior to the addition of said alkaline filler to the paper mix.

2. In the manufacture of paper filled with alkaline filler wherein alkaline filler is added to a paper mix under conditions favoring the minimizing of the time and/or intimacy of contact of the constituents of the mix, that step comprising effecting the precipitation in the presence of said alkaline filler of a precipitable material and a precipitant therefor just prior to the addition of said alkaline filler to the paper mix.

3. In the manufacture of paper filled with alkaline filler wherein alkaline filler is added to a paper mix under conditions favoring the minimizing of the time and/or intimacy of contact of the constituents of the mix, the steps comprising effecting the precipitation in the presence of said alkaline filler of a precipitable material and a precipitant therefor, and adding a further quantity of precipitant just prior to the addition of said alkaline filler to the paper mix.

4. In the manufacture of paper filled with alkaline filler wherein alkaline filler comprising calcium carbonate is added to a paper mix under conditions favoring the minimizing of the time and/or intimacy of contact of the constituents of the mix, that step comprising eifectin the precipitation in the presence of said al raline filler of a precipitable material and a precipitant therefor just prior to the addition of said alkaline filler to the paper mix.

5. In the manufacture of paper filled with alkaline filler wherein alkaline filler coinprising calcium carbonate and magnesium compound is added to a paper mix under conditions favoring the minimizing of the time and/or intimacy of contact of the constituents of the mix, that step comprising effecting the precipitation in the presence of said alkaline filler of a precipitable material I and a precipitant therefor just prior to the addition of said alkaline filler to the paper mix.

6. In the manufacture of paper filled with alkaline filler wherein alkaline filler comprising calcium carbonate magnesium hydroxide is added to a paper mix under conditions favoring the minimizing of the time and/or intimacy of contact of the constituents of the mix, that step comprising effecting the precipitation in the presence of said alkaline filler of a precipitable material and a precipitant therefor just prior to the addition of said alkaline filler to the paper mix.

7. In the manufacture of paper filled with alkaline filler wherein alkaline filler is added to a paper mix under conditions favoring the minimizing of the time and/or intimacy of contact of the constituents of the mix, that step comprising effecting the precipitation in the presence of said alkaline filler of a precipitable material comprising size and a precipitant therefor just prior to the addition of said alkaline filler to the paper mix.

' 8. In the manufacture of paper filled with alkaline filler wherein alkaline filler is added to a paper mix under conditions favoring the minimizing of the time and/or intimacy of contact of the constituents of the mix, that step comprising effecting the precipitation in the presence of said alkaline filler of a precipitable material comprising rosin size and a precipitant therefor just prior to the addition of said alkaline filler to the paper mix.

9. In the manufacture of paper filled with alkaline filler wherein alkaline filler is added the presence 0 to a paper mix under conditions favoring the minimizing of the time and/or intimacy of contact of the constituents of the mix, that step comprisin effecting the precipitation in the presence 0% said alkaline filler of a precipitable material and a precipitant therefor comprising acidic material just prior to the addition of said alkaline filler to the paper flux.

10. In the manufacture of paper filled with alkaline filler wherein alkaline filler is added to a paper mix under conditions favoring the minimizing of the time and/or intimacy of contact of the constituents of the mix, that step comprisin effecting the precipitation in %said alkaline filler of a precipitable material and a precipitant therefor comprising metallic salt just prior to the addition of said alkaline filler to the paper mix.

11. In the manufacture of paper filled with alkaline filler wherein alkaline filler is added to a paper mix under conditions favoring the minimizing of the time and/or intimacy of contact of the constituents of the mix, that step comprising effecting the precipitation in the presence of said alkaline filler of a precipitable material and a precipitant therefor comprising aluminum compound just prior to the addition of said alkaline filler to the paper mix.

' 12. In the manufacture of paper filled with alkaline filler wherein alkaline filler is added to a paper mix under conditions favoring the minimizing of the time and/or intimacy of contact of the constituents of the mix, that step comprising effecting the precipitation in the presence of said alkaline filler of a precipitable material and a precipitant therefor comprising alum just prior to the addition of said alkaline filler to the paper mix.

13. In the manufacture of paper filled with alkaline filler wherein alkaline filler is added to a paper mix under conditions favoring the minimizing of the time and/or intimacy of contact of the constituents of the mix, that step comprising effecting the precipitation in the presence of said alkaline filler of a precipitable material comprising size and a precipitant therefor comprising acidic material just prior to the addition of said alkaline filler to the paper mix.

14. In the manufacture of paper filled with alkaline filler wherein alkaline filler is added to a paper mix under conditions favoring the minimizing of the time and/or intimacy of contact of the constituents of the mix, that step comprising effecting the precipitation in the presence of said alkaline filler of a precipitable material comprising size and a precipitant therefor comprising metallic salt just prior to the addition of said alkaline filler to the paper mix.

15. In the manufacture of paper filled with alkaline filler wherein alkaline filler is added to a paper mix under conditions favoring the minimizing of the time and/or intimacy of contact of the constituents of the mix, that the minimizing of the time and/or intimacy of contact of the constituents of the mix, that step comprising effecting the precipitation in the presence of said alkaline filler of a precipitable material comprising size and a precipitant therefor comprising alum just prior to the addition of said alkaline filler to the paper mix.

17. In the manufacture of paper filled with i alkaline filler wherein alkaline filler is added to a paper mix under conditions favoring the minimizing of the time and/or intimacy of contact'of the constituents of the mix, that step comprising effecting the precipitation in the presence of said alkaline filler of a precipitable material comprising rosin size and a precipitant therefor comprising alum just prior to the addition of said alkaline filler to the paper mix.

18. The method of treating alkaline filler comprising eft'ectin the precipitation in the presence thereof 0 a precipitable material and a precipitant therefor just prior to the the inclusion of said alkaline filler in a paper mix.

19. The method of treating alkaline filler comprising eifecting the precipitation in the presence thereof of a precipitable material and a precipitant therefor and adding a fur ther quantity of a precipitant just prior to the inclusion of said alkaline filler in a paper mix.

20. The method of treating alkaline filler comprising effecting the precipitation in the presence thereof of a precipitable material and a precipitant therefor in an aqueous med1um ust prior to the inclusion of said alkaline filler in a paper mix.

21. The step in a process of manufacturing paper filled with alkaline filler comprising adding to a paper mix an alkaline filler temporarily protected with a coating precipitated on the particles thereof.

22. The step in a process of manufacturing paper filled with alkaline filler comprising adding to a paper mix an alkaline filler in contact with water temporarily protected with a coating precipitated on the particles thereof.

23. The step in a process of manufacturing pa er filled with alkaline filler comprising adding to a paper mix an alkaline filler temporarily protected with an acidic coating precipitated on the particles thereof.

24. The step in a process of manufacturing paper filled with alkaline filler comprising adding to a paper mix an alkaline filler with a temporarily lowered pH, protected by a coatin newly precipitated on the particles thereof.

In testimony whereof I aflix my signature.

HAROLD ROBERT RAFTON. 

